Sweeping Into Action

This week we deployed a sampling team of 5 to set up 3 sites for standardized sampling at rare Charitable Research Reserve in Cambridge. Four colleagues and I set out early Monday morning to get started on our days’ work. I was eager to get back out to the field and set up some traps. For a few of our crew members it was their first time preparing the array of traps for our standardized sampling.

This is a picture of me taking some GPS coordinates at one of our sampling sites. This site was located in a hard wood forest, dominated by maple trees

So there were great learning opportunities and I really enjoyed showing some of what I had learned last summer aboard the BIObus. By the end of the day everyone had learned our routine and we were all working efficiently together. I can confidently say that everyone was enjoying themselves on our first day out as a big group, we had good weather and everything went smoothly.

Part of standardized sampling is sweep netting. We use a butterfly nets to “sweep” through the vegetation close to the ground. This technique targets both flying and sedentary insects found on vegetation such as caterpillars and sawfly larvae (order: Lepidoptera and Hymenoptera). As we swing our nets through vegetation it knocks the arthropods into our nets while the constant sweeping motion keeps them trapped inside at that back of the net. This affords us the convenience of insects flying right into the path of our nets as we disturb them from their cryptic hiding places. When sweeping sites we try to encompass the entire site, sweeping through all vegetation types in efforts to capture a greater diversity.

Here again at our hardwood forest site, Dan (left) and Shannon (right) are sweeping the understory for insects. Sweep netting is part of our standardized sampling protocol, where we net insects for 5 minutes

Many insects and arthropods are host specific or are associated with only a small hand full of plants. If I were to sweep through long green grass I would expect the see a lot of treehoppers (Membracidae), planthoppers (Fulgoroidea), and leafhoppers (Cicadellidae). This was all to true when we swept two of our sampling sites that are dominated by grasses. The abundance of these hemipterans, true bugs, was astounding. With our aspirators we were literally removing handfuls of insects from our nets. These sweeps provided the largest samples I have ever taken with a sweep net. Our last site is located in a hard wood forest dominated by maples. In comparison to the grass sites I would not expect to find the same abundance of hoppers, rather there is commonly a greater abundance of flies. The sweeps of the forest site produced just that. We netted a huge mass of mosquitos and crane flies. In retrospect all of the sweeps this far at Rare have proved to be highly productive and have surpassed in biomass anything in sweep nets that I have done previously.

After we sweep for 5 minutes he have to empty the insects and other arthropods of our nets. From left to right, you can see me aspirating along with Josh who has his entire head in the net to get better access at the insects deep in his net, and Dan is preparing to empty the insects he has aspirated from his net

As mentioned above we use aspirators to collect the arthropods from inside of our nets. An aspirator allows you to collect small insects with ease in comparison to your fingers or forceps. When aspirating you are actually creating a vacuum by gently inhaling on a hose that’s attached to a glass vial, where by the insects gets sucked up directly into the holding vial. Luckily, there is a fine mesh layer preventing the insects from entering your mouth. I am aspirating in the third picture, you can see the tube that I use in my mouth to create the sucking action required to capture the netted insects. Josh, in the middle of the same picture is employing a classic technique. He is also aspirating his sweep net but he is doing so with his head completely inside the net. This helps to prevent the flying insects caught from escaping while we are aspirating. Beside Josh is Dan, who is inspecting the container he has filled with his aspirator, possibly in awe like I was from the massive abundance of arthropods caught.

Of Bugs and Men

Of Bugs and Men

This past week wasn’t a mundane week by any means. Setting out at 9am on a Monday morning, Danielle, Dan, Josh, Nate and I set out for Cambridge, Ontario to get samples of the insects inhabiting the Waterloo region. Our destination: the rare Charitable Research Reserve. The rare Charitable Research Reserve (rare) supports some of southern Ontario’s richest biodiversity. Nestled among 900 acres of floodplains, croplands, limestone alvars, cliffs, coniferous and deciduous forests, Rare is one of the meeting points of the Carolinian and Northern Hardwood forest zones. With a wide variety of habitats available, rare is without a doubt a prime spot for catching all kinds of interesting arthropods.

Since arthropods are so diverse, the first two things you need to collect a good sample is creativity and persistence. This week we used six different methods of trapping: Berlese funnels, flight intercept traps, pan traps, Malaise traps, pitfall traps and sweep nets.

Here we have two Berlese funnels. One contains decomposing wood, while the other has an assortment of oak and maple leaf litter

Berlese funnels are used for trapping arthropods that live in the dirt or on the ground. These traps are made by gathering samples of soil, moss and leaf litter and placing them in large funnels above small containers full of ethanol. The principle behind these traps is that arthropods living just above and below the ground normally strongly dislike light. Since the large end of the funnel is exposed to light, arthropods travel downwards seeking the cool comfort of darkness. As the funnel constricts at the base, they are forced to burrow towards the smaller opening and eventually meet their fate dropping into the jar of ethanol.

Although the pan trap was only set up maybe a minute before this picture was taken, we had already caught a nice big spider!

Pan traps also help to catch ground-dwelling insects as well as insects attracted to colourful plants. Usually painted with primary colours, pan traps are bowls filled with soapy water. Each pan trap tends to attract slightly different insects as the colours mimic different food sources. As the insect approaches the bowl, it either falls into or gets caught in the soapy water. The soap in the water helps to break the surface tension preventing the insect from floating above the surface unharmed.

For a third kind of trap targeted to ground-dwellers, pitfall traps are designed just like they are named. A small pit is dug and a similarly sized cup filled with soapy water is placed inside the pit. Insects crawling over the ground stumble onto the lip of the pit and end up falling in. Since the sides of the cup are not smooth, the insects cannot crawl back out and get trapped.

A pitfall trap. The clear lid is used to help prevent leaves and rain from disturbing the sample

If you are a regular reader of the blog, you may have previously read about the Malaise traps used in the School Malaise Trap Program. Malaise traps look like small sloped tents with a black lower half and a white upper half. The idea is that insects fly into the tent and – drawn to the lighter upper half – end up moving to the peak of the tent. At the top end of the tent is a bottle filled with ethanol that traps and stores the insects.

A Malaise trap in action. In the background you can see a group of wild students sifting through the insects captured in their sweep net

Similar to Malaise traps, flight intercept traps are designed to collect other airborne insects. A long piece of screen is extended between two trees. If you can imagine what happens when you run full speed into a volleyball net, you may have an idea of how these traps work. Unsuspecting insects hit the trap mid-flight and fall into a pool of soapy water laid out at the base.

An intercept trap set up on the edge of a forest

Last but not least, we spent a portion of the day sweep netting arthropods with giant burlap nets. This way we were able to capture some of the more evasive arthropods like spiders, beetles and hymenopterans. (If you’d like to hear more about our sweep netting, be sure to check out Nate’s blog this week!)

In full sweep netting mode. You can see the determination in my stance